Ammoxidation catalyst composition, and process for producing acrylonitrile or methacrylonitrile using the same

ABSTRACT

Disclosed is an ammoxidation catalyst composition for use in producing acrylonitrile from propylene, or methacrylonitrile from isobutene or tert-butanol, by ammoxidation of the propylene or of the isobutene or tert-butanol, comprising an oxide catalyst composition represented by the formula: 
     
         Mo.sub.12 (Bi.sub.1-a A.sub.a).sub.b Fe.sub.c Ni.sub.d X.sub.e Y.sub.f 
    
      O g , 
     wherein 
     A is at least one rare earth element, 
     X is at least one element selected from magnesium and zinc, 
     Y is at least one element selected from potassium, rubidium and cesium, 
     a is a number of from 0.6 to 0.8, 
     b is a number of from 0.5 to 2, 
     c is a number of from 0.1 to 3, 
     d is a number of from 4 to 10, 
     e is a number of from 0 to 3, 
     f is a number of from 0.01 to 2, and 
     g is a number determined by the valence requirements of the other elements present. 
     By use of the ammoxidation catalyst composition of the present invention, not only can acrylonitrile and methacrylonitrile be produced in high yield, but also a lowering of the yield of acrylonitrile or methacrylonitrile can be effectively suppressed even after the operation of the production process has been conducted for a prolonged period of time.

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/530,288 filed on Sep. 21, 1995, now abandoned, which is a371 of PCT/JP94/01312 filed Aug. 9, 1994.

BACKGROUND OF THE INVENTION

1. Technical field

The present invention relates to an ammoxidation catalyst composition,and a process for producing acrylonitrile or methacrylonitrile using thesame. More particularly, the present invention is concerned with anammoxidation catalyst composition for use in the process for producingacrylonitrile or methacrylonitrile by reacting propylene with, orreacting isobutene or tert-butanol with a molecular oxygen-containinggas and ammonia, the ammoxidation catalyst composition comprising anoxide catalyst composition comprised of molybdenum, bismuth, at leastone rare earth element, iron, nickel, at least one element selected frommagnesium and zinc, and at least one element selected from potassium,rubidium and cesium, wherein the atomic ratio of the sum of bismuth andthe at least one rare earth element, relative to twelve atoms ofmolybdenum, is from 0.5 to 2 and the atomic ratio of the at least onerare earth element to the sum of bismuth and the at least one rare earthelement is from 0.6 to 0.8. By use of such an ammoxidation catalystcomposition, not only can acrylonitrile or methacrylonitrile be producedin high yield, but also a lowering of the yield of acrylonitrile ormethacrylonitrile can be effectively suppressed even after the operationof the production process has been conducted for a prolonged period oftime. The present invention is also concerned with a process forproducing acrylonitrile or methacrylonitrile using such an ammoxidationcatalyst composition.

2. Prior Art

It has been well known to produce acrylonitrile or methacrylonitrile byammoxidation of propylene, or of isobutene or tert-butanol, namely, areaction of propylene with, or of isobutene or tert-butanol with amolecular oxygen-containing gas and ammonia. A number of proposals havebeen made with respect to catalysts for use in the ammoxidation ofpropylene, or of isobutene or tert-butanol. For example, U.S. Pat. No.3,226,422 proposes an oxide catalyst containing molybdenum, bismuth andiron, and Examined Japanese Patent Application Publication No. 38-19111proposes an oxide catalyst containing antimony and iron. Further,various improvements have been proposed with respect to theseammoxidation catalyst systems.

For example, each of British Patent No. 1,445,512 and U.S. Pat. No.4,746,753 discloses a catalyst containing an alkali metal and thalliumin addition to molybdenum, bismuth and cerium. Examined Japanese PatentApplication Publication No. 61-43094 discloses a catalyst comprisingmolybdenum, tungsten, bismuth and cerium. U.S. Pat. No. 4,969,390discloses an oxide catalyst containing at least one element selectedfrom iron, chromium, aluminum and bismuth, in addition to molybdenum,tellurium and cerium. U.S. Pat. No. 4,192,776 discloses an oxidecatalyst containing, in addition to molybdenum, bismuth and iron, atleast one element selected from nickel and cobalt, and at least oneelement selected from an alkali metal, a rare earth element, tantalumand niobium. U.S. Pat. No. 4,443,556 discloses an oxide catalystcontaining molybdenum, bismuth and iron as essential elements, and alsocontaining at least one element selected from cerium, lanthanum,neodymium, praseodymium, samarium, europium and gadolinium, and at leastone element selected from potassium, rubidium and cesium. UnexaminedJapanese Patent Application Laid-Open Specification No. 59-204163discloses a catalyst containing, in addition to molybdenum, bismuth,phosphorus and silicon, at least two elements selected from iron,cobalt, nickel, copper, zirconium and potassium, and at least oneelement selected from manganese, cerium, thorium, yttrium, lanthanum andthallium. However, in the above prior art documents, there are noworking examples using a catalyst composition satisfying the specificrequirements of the catalyst composition of the present invention.

Further, each of U.S. Pat. No. 5,093,299, U.S. Pat. No. 5,175,334 andU.S. Pat. No. 5,212,137 discloses a catalyst containing molybdenum,bismuth, iron, nickel, magnesium, potassium and cesium as essentialelements and optionally containing cobalt, manganese, chromium,phosphorus, antimony, tellurium, sodium, cerium and/or tungsten, and aprocess for producing acrylonitrile or methacrylonitrile using such acatalyst. However, it is noted that in the working examples of the abovethree U.S. patent documents, a catalyst containing cerium is not used.It is needless to say that, in these patent documents, neither workingexample nor description is found with respect to use of any other rareearth element.

The catalysts disclosed in the above-mentioned patent documents aregreatly improved in respect of the yield of acrylonitrile ormethacrylonitrile at the initial stage of reaction. However, thosecatalysts are still unsatisfactory in respect of the yield ofacrylonitrile or methacrylonitrile when the operation of the productionprocess is conducted for a prolonged period of time.

DISCLOSURE OF THE INVENTION

In the above situations, the present inventors have made extensive andintensive studies toward developing a catalyst for use in ammoxidation,which is free from the above-mentioned problem, and which can beadvantageously used not only for producing acrylonitrile ormethacrylonitrile in high yield, but also for performing a stableammoxidation reaction even when the operation of the production processis conducted for a prolonged period of time, so that a lowering of theyield of acrylonitrile or methacrylonitrile is small. As a result, ithas been found that when an oxide catalyst composition, which isrepresented by the formula (I):

    Mo.sub.12 (Bi.sub.1-a A.sub.a).sub.b Fe.sub.c Ni.sub.d X.sub.e Y.sub.f O.sub.g                                                   (I)

wherein:

A is at least one rare earth element,

X is at least one element selected from magnesium and zinc,

Y is at least one element selected from potassium, rubidium and cesium,

a is the atomic ratio of A to the sum of bismuth and A,

b is the atomic ratio of the sum of bismuth and A, relative to twelveatoms of molybdenum, and

c, d, e, f and g are, respectively, the atomic ratios of iron, nickel,X, Y and oxygen, relative to twelve atoms of molybdenum,

wherein

a is a number of from 0.6 to 0.8,

b is a number of from 0.5 to 2,

c is a number of from 0.1 to 3,

d is a number of from 4 to 10,

e is a number of from 0 to 3,

f is a number of from 0.01 to 2, and

g is a number determined by the valence requirements of the otherelements present,

is used as an ammoxidation catalyst in the process for producingacrylonitrile or methacrylonitrile by reacting propylene with, orreacting isobutene or tert-butanol with a molecular oxygen-containinggas and ammonia, not only can acrylonitrile or methacrylonitrile beproduced in high yield, but also the ammoxidation reaction can be stablyconducted even when the operation of the production process is conductedfor a prolonged period of time, so that a lowering of the yield ofacrylonitrile or methacrylonitrile is very small. The present inventionhas been made, based on this novel finding.

Accordingly, it is an object of the present invention to provide anammoxidation catalyst composition, by use of which not only canacrylonitrile or methacrylonitrile be produced in high yield, but alsothe ammoxidation reaction can be stably conducted even when theoperation of the production process is conducted for a prolonged periodof time, so that a lowering of the yield of acrylonitrile ormethacrylonitrile is very small.

It is another object of the present invention to provide a process forproducing acrylonitrile or methacrylonitrile using the above-mentionednovel ammoxidation catalyst composition.

The foregoing and other objects, features and advantages of the presentinvention will be apparent from the following detailed description andappended claims.

DETAILED DESCRIPTION OF THE INVENTION

In one aspect of the present invention, there is provided anammoxidation catalyst composition comprising an oxide catalystcomposition represented by the formula (I):

    Mo.sub.12 (Bi.sub.1-a A.sub.a).sub.b Fe.sub.c Ni.sub.d X.sub.e Y.sub.f O.sub.g                                                   (I)

wherein:

A is at least one rare earth element,

X is at least one element selected from magnesium and zinc,

Y is at least one element selected from potassium, rubidium and cesium,

a is the atomic ratio of A to the sum of bismuth and A,

b is the atomic ratio of the sum of bismuth and A, relative to twelveatoms of molybdenum, and

c, d, e, f and g are, respectively, the atomic ratios of iron, nickel,X, Y and oxygen, relative to twelve atoms of molybdenum,

wherein

a is a number of from 0.6 to 0.8,

b is a number of from 0.5 to 2,

c is a number of from 0.1 to 3,

d is a number of from 4 to 10,

e is a number of from 0 to 3,

f is a number of from 0.01 to 2, and

g is a number determined by the valence requirements of the otherelements present.

The ammoxidation catalyst composition of the present invention has acharacteristic feature in that the atomic ratio b of the sum of bismuthand A, relative to twelve atoms of molybdenum, is from 0.5 to 2,preferably 0.7 to 1.8, and the atomic ratio a of A to the sum of bismuthand A is from 0.6 to 0.8. When b is less than 0.5 or is more than 2, notonly does the yield of acrylonitrile or methacrylonitrile at the initialstage of reaction become low, but also the ammoxidation reaction becomesunstable. When a is less than 0.6, although the yield of acrylonitrileor methacrylonitrile is good at the initial stage of reaction, not onlyis the ammoxidation reaction unstable but the yield of acrylonitrile ormethacrylonitrile is also drastically lowered with the lapse ofoperation time. On the other hand, when a is more than 0.8, the yield ofacrylonitrile or methacrylonitrile is disadvantageously lowered even atthe initial stage of reaction. A is at least one rare earth element. Bythe term "at least one rare earth element" are meant one or moreelements selected from the group consisting of scandium, yttrium,lanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium and lutetium, which are classified as rare earth elements inthe Periodic Table. Of the above-mentioned rare earth elements, yttrium,lanthanum, cerium, praseodymium, neodymium and samarium are preferred.Cerium is more preferred. With respect to c, d, e and f, which are,respectively, the atomic ratios of iron, nickel, X (which is at leastone element selected from magnesium and zinc) and Y (which is at leastone element selected from potassium, rubidium and cesium), relative totwelve atoms of molybdenum, c is from 0.1 to 3, preferably from 0.5 to2.5; d is from 4 to 10, preferably from 5 to 8; e is from 0 to 3,preferably from 0.1 to 2.5; and f is from 0.01 to 2, preferably from0.02 to 1.

With respect to a carrier which can be used to support thereon the oxidecatalyst composition of the present invention, oxides, such as silica,alumina, titania and zirconia, can be employed. Of these oxides, silicais preferred. Silica is inherently inert, differing from other carriermaterials, and can serve as an excellent binder for the ingredients ofthe oxide catalyst composition without impairing the selectivity of theoxide catalyst composition and serve to impart the resulting catalystcomposition with a high attrition resistance. The amount of carrier tobe used may be in the range of 30 to 70% by weight, preferably 40 to 60%by weight, based on the total weight of the oxide catalyst compositionand the carrier.

The ammoxidation catalyst composition of the present invention can beproduced by a conventional method. For example, the ammoxidationcatalyst composition can be produced by a method comprising the steps of(1) preparing a slurry of starting materials, (2) spray-drying theslurry prepared in step (1) above to obtain a dried particulate catalystprecursor, and (3) subjecting the dried particulate catalyst precursorobtained in step (2) above to calcination and firing, successively.

Hereinbelow, explanation is made with respect to a preferred embodimentof the above-mentioned method for producing the ammoxidation catalystcomposition of the present invention, which comprises steps (1), (2) and(3), above.

In step (1), a slurry of starting materials is prepared. In the startingmaterials, each of the elements (which are to be incorporated into acatalyst composition), i.e., molybdenum, bismuth, at least one rareearth element, iron, nickel, magnesium, zinc, potassium, rubidium andcesium, may be present in the form of an ammonium salt, a nitrate, achloride, a sulfate and/or an organic acid salt, which are soluble inwater or nitric acid. Especially, it is preferred that a molybdenumsource be in the form of an ammonium salt, and that each of bismuth, atleast one rare earth element, iron, nickel, magnesium, zinc, potassium,rubidium and cesium be used in the form of a nitrate.

As mentioned above, in the ammoxidation catalyst composition of thepresent invention, an oxide, such as silica, alumina, titania orzirconia, can be employed as a carrier for the oxide catalystcomposition represented by formula (I). Of the above oxides, silica ismost advantageously used. As the source of silica, a silica sol ispreferred.

The slurry of starting materials can be prepared by, for example, addinga solution of nitrates of component metals except molybdenum (i.e.,sources of bismuth, at least one rare earth element, iron, nickel,magnesium, zinc, potassium, rubidium and cesium) in water or in aqueousnitric acid to a silica sol, followed by addition of an aqueous ammoniummolybdate solution. Alternatively, for preparing the slurry of startingmaterials, the above-mentioned aqueous ammonium molybdate solution maybe first added to a silica sol, followed by addition of theabove-mentioned solution of nitrates of component metals exceptmolybdenum.

In step (2), the slurry obtained in step (1) above is subjected to spraydrying, to thereby obtain a quasispherical particulate catalystprecursor. The spray drying of the slurry can be generally conducted bycentrifugation, two-phase flow nozzle method or high pressure nozzlemethod to obtain a dried particulate catalyst precursor.

In this instance, it is preferred to use air which has been heated by anelectric heater, steam or the like, as a heat source for drying. In thiscase, it is preferred that the temperature at an entrance to the dryerof the spray dryer be from 100° to 400° C., preferably 150° to 300° C.

In step (3), the dried particulate catalyst precursor obtained in step(2) above is calcined and finally fired to thereby obtain a desiredoxide catalyst composition. The dried particulate catalyst is calcinedat a temperature of from 150° to 500° C., and then subjected to firingat a temperature of from 500° to 750° C., preferably 550° to 700° C. for1 to 20 hours. For the calcination and firing, a kiln, such as a rotarykiln, a tunnel kiln or a muffle kiln, can be used.

When the ammoxidation catalyst composition of the present inventioncomprises an oxide catalyst composition supported on a carrier(preferably silica), it is preferred that the particle diameterdistribution of the ammoxidation catalyst composition be within therange of from 10 to 150 μm.

The process for producing acrylonitrile or methacrylonitrile by reactingpropylene with, or reacting isobutene or tert-butanol with a molecularoxygen-containing gas and ammonia in the presence of an ammoxidationcatalyst composition of the present invention may be conducted either ina fluidized bed reactor or in a fixed bed reactor. However, a fluidizedbed reactor is preferred.

Propylene, or isobutene or tert-butanol and ammonia to be used in theprocess of the present invention need not necessarily be of so highpurity but may be of a commercial grade. As a source of oxygen, air isusually employed. Gas having an increased oxygen content, such as agaseous mixture of air and oxygen, is also usable.

In the process of the present invention, it is advantageous that themolar ratios of propylene, or isobutene or tert-butanol:ammonia:air bein the range of 1:0.8 to 1.4:7 to 12, preferably 1:0.9 to 1.3:8 to 11.The reaction temperature may be 350° to 550° C., preferably 400° to 500°C. The reaction may usually be conducted under a pressure of fromatmospheric pressure to a pressure of 3 atm. The time of contact betweengaseous mixture of the raw materials and the catalyst composition(contact time) may be from 0.5 to 20 sec·g/cc, preferably from 1 to 10sec·g/cc.

Thus, in another aspect of the present invention, there is provided aprocess for producing acrylonitrile from propylene, or methacrylonitrilefrom isobutene or tert-butanol, by ammoxidation of the propylene or ofthe isobutene or tert-butanol, which comprises reacting propylene with,or reacting isobutene or tert-butanol with a molecular oxygen-containinggas and ammonia at a temperature of from 350° C. to 550° C. under apressure of from atmospheric pressure to 3 atm in the presence of anammoxidation catalyst composition comprising an oxide catalystcomposition represented by the formula (I):

    Mo.sub.12 (Bi.sub.1-a A.sub.a).sub.b Fe.sub.c Ni.sub.d X.sub.e Y.sub.f O.sub.g                                                   (I)

wherein:

A is at least one rare earth element,

X is at least one element selected from magnesium and zinc,

Y is at least one element selected from potassium, rubidium and cesium,

a is the atomic ratio of A to the sum of bismuth and A,

b is the atomic ratio of the sum of bismuth and A, relative to twelveatoms of molybdenum, and

c, d, e, f and g are, respectively, the atomic ratios of iron, nickel,X, Y and oxygen, relative to twelve atoms of molybdenum,

wherein

a is a number of from 0.6 to 0.8,

b is a number of from 0.5 to 2,

c is a number of from 0.1 to 3,

d is a number of from 4 to 10,

e is a number of from 0 to 3,

f is a number of from 0.01 to 2, and

g is determined by the valence requirements of the other elementspresent.

As mentioned above, by use of the ammoxidation catalyst composition ofthe present invention in the process for producing acrylonitrile ormethacrylonitrile by reacting propylene with, or reacting isobutene ortert-butanol with a molecular oxygen-containing gas and ammonia, notonly can acrylonitrile or methacrylonitrile be produced in high yield,but also the ammoxidation reaction can be stably conducted for aprolonged period of time, so that even after the operation of theproduction process has been conducted for a period of time as long asabout one month, a lowering of the yield of acrylonitrile ormethacrylonitrile is as small as 0.5% or less, relative to the yield ofacrylonitrile or methacrylonitrile at the initial stage of reaction.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, the present invention will be described in more detail withreference to the following Examples and Comparative Examples, but theyshould not be construed as limiting the scope of the present invention.

In the following Examples and Comparative Examples, the conversion andyield used for evaluating the results of the reaction are defined asfollows: ##EQU1##

A stainless steel (SUS 304) fluidized bed reactor having an outerdiameter of 3 inches was used as a reaction apparatus. The reactionpressure (P) was maintained at 0.5 kg/cm² ·G, and the reactiontemperature (T) was maintained at 430° C. The amount (W) of a catalystcharged in the reactor was 1,000 to 2,000 g, and the total flow rate (F)of raw material gases introduced into the reactor was 100 to 150 cc/secin terms of the volume per unit time under normal temperature andpressure (N.T.P) conditions.

The contact time is defined by the following formula:

Contact time (sec·g/cc)=(W/F)×273/(273+T)×(1.03+P)/1.03.

The compositions of raw material gases introduced into the reactor wereas follows:

for an ammoxidation reaction of propylene:

    propylene/ammonia/air=1/1.1/8.0-10.0.

for an ammoxidation reaction of isobutene or tert-butanol:

    isobutene or tert-butanol/ammonia/air=1/1.2/9.0-10.5.

EXAMPLE 1

An ammoxidation catalyst composition, composed of oxides supported on50% by weight, based on the total weight of the oxides and silica, ofsilica, having a structure represented by the formula:

    Mo.sub.12 Bi.sub.0.20 Ce.sub.0.40 Fe.sub.2.0 Ni.sub.5.6 Mg.sub.2.2 K.sub.0.07 Cs.sub.0.04,

was prepared as follows.

38.6 g of bismuth nitrate [Bi(NO₃)₃ ·5H₂ O], 69.0 g of cerium nitrate[Ce(NO₃)₃ ·6H₂ O], 321.2 g of iron nitrate [Fe(NO₃)₃ ·9H₂ O], 647.6 g ofnickel nitrate [Ni(NO₃)₂ ·6H₂ O], 224.2 g of magnesium nitrate [Mg(NO₃)₂·6H₂ O], 2.82 g of potassium nitrate [KNO₃ ] and 3.10 g of cesiumnitrate [CsNO₃ ] were dissolved in 755.4 g of a 17.9 wt % aqueous nitricacid solution. The resultant solution was added to 3,333.4 g of a silicasol having a SiO₂ content of 30 wt %, to obtain a mixture. To the thusobtained mixture was added a solution of 842.4 g of ammoniumparamolybdate [(NH₄)₆ Mo₇ O₂₄ ·4H₂ O] in 1,696.6 g of water, to therebyobtain a slurry. The slurry thus obtained was fed to a parallel flowtype spray-drying apparatus, in which the slurry was atomized by meansof a sprayer having a dish type rotor disposed above the central portionof a dryer of the spray-drying apparatus, and dried at about 200° C., tothereby obtain a dried particulate catalyst precursor. The obtaineddried particulate catalyst precursor was calcined in an electric kiln at400° C. for 1 hour and then subjected to firing at 590° C. for 2 hours,thereby obtaining a catalyst composition supported on the silica.

Using 1,400 g of the obtained catalyst composition supported on thesilica, an ammoxidation reaction of propylene was conducted. The contacttime in the ammoxidation was 6.7 sec·g/cc. Results of the reaction wereevaluated at time points of 100 hours, 700 hours and 1,400 hours afterthe start of reaction. As a result, it was found that, 100 hours afterthe start of reaction, the conversion of propylene was 99.8%, and theyield of acrylonitrile was 80.8%; that, 700 hours after the start ofreaction, the conversion of propylene was 99.7%, and the yield ofacrylonitrile was 80.5%; and that, 1,400 hours after the start ofreaction, the conversion of propylene was 99.6%, and the yield ofacrylonitrile was 80.2%.

EXAMPLES 2 TO 13 AND COMPARATIVE EXAMPLES 1 TO 4

Ammoxidation catalyst compositions, composed of oxides supported on 50%by weight, based on the total weight of the oxides and silica, ofsilica, having the respective compositions indicated in Table 1 wereprepared in substantially the same manner as in Example 1. Using theobtained catalyst compositions individually, ammoxidation reactions ofpropylene were conducted. Results are shown in Table 1.

                                      TABLE 1    __________________________________________________________________________            Mo  Bi A        Fe  Ni X    Y        a  b    __________________________________________________________________________    Example 1            12  0.20                   Ce 0.40  2.0 5.6                                   Mg 2.2                                        K 0.07                                            Cs 0.04                                                 0.67                                                    0.60    Example 2            12  0.45                   Ce 0.90  1.8 5.0                                   Mg 2.0                                        K 0.09                                            Rb 0.05                                                 0.67                                                    1.35    Example 3            12  0.45                   Ce 0.90  1.8 5.0                                   Zn 2.0                                        K 0.09                                            Rb 0.05                                                 0.67                                                    1.35    Example 4            12  0.60                   Ce 1.20  1.6 4.8                                   Mg 1.9                                        K 0.11                                            Rb 0.05                                                 0.67                                                    1.80    Example 5            12  0.27                   Ce 1.08  1.8 5.0                                   Mg 2.0                                        K 0.11                                            Cs 0.03                                                 0.80                                                    1.35    Example 6            12  0.54                   Ce 0.81  1.8 7.0                                   Mg 0 K 0.10                                            Rb 0.04                                                 0.60                                                    1.35    Example 7            12  0.34                   Ce 1.01  2.2 4.1                                   Mg 2.5                                        K 0.20   0.75                                                    1.35    Example 8            12  0.45                   Ce 0.90  1.8 5.0                                   Mg 2.0                                        Rb 0.15  0.67                                                    1.35    Example 9            12  0.39                   Ce 0.96  2.0 5.3                                   Mg 1.5                                        Cs 0.13  0.71                                                    1.35    Example 10            12  0.30                   Y 0.60   2.0 5.4                                   Mg 2.1                                        K 0.09                                            Rb 0.05                                                 0.67                                                    0.90    Example 11            12  0.30                   La 0.60  2.0 5.4                                   Mg 2.1                                        K 0.09                                            Rb 0.05                                                 0.67                                                    0.90    Example 12            12  0.30                   Pr 0.13                        Nd 0.47                            2.0 5.4                                   Mg 2.1                                        K 0.09                                            Rb 0.05                                                 0.67                                                    0.90    Example 13            12  0.30                   Sm 0.6   2.0 5.4                                   Mg 2.1                                        K 0.09                                            Rb 0.05                                                 0.67                                                    0.90    Comp. Ex. 1            12  0.83                   Ce 1.67  1.5 4.1                                   Mg 1.6                                        K 0.09                                            Rb 0.05                                                 0.67                                                    2.50    Comp. Ex. 2            12  1.35                   0        2.0 5.5                                   Mg 2.2                                        K 0.09                                            Rb 0.05                                                 0  1.35    Comp. Ex. 3            12  0.68                   Ce 0.68  1.8 5.0                                   Mg 2.0                                        K 0.09                                            Rb 0.05                                                 0.50                                                    1.36    Comp. Ex. 4            12  0.14                   Ce 1.21  1.8 5.0                                   Mg 2.0                                        K 0.09                                            Rb 0.05                                                 0.90                                                    1.35    __________________________________________________________________________           Temperature Results obtained                                  Results obtained                                             Results obtained           (°C.) for                  Contact                       100 hrs after                                  700 hrs after                                             1400 hrs after           firing of                  time the start of reaction                                  the start of reaction                                             the start of reaction           catalyst                  (sec · g/                       Conversion                             Yield                                  Conversion                                        Yield                                             Conversion                                                   Yield           composition                  cc)  (%)   (%)  (%)   (%)  (%)   (%)    __________________________________________________________________________    Example 1           590    6.0  99.8  80.8 99.7  80.5 99.6  80.2    Example 2           610    6.7  99.8  82.0 99.7  81.8 99.7  81.8    Example 3           610    6.7  99.7  81.9 99.7  81.7 99.6  81.6    Example 4           590    6.2  99.8  81.6 99.7  81.4 99.5  81.3    Example 5           600    6.4  99.7  81.4 99.6  81.2 99.5  80.9    Example 6           610    6.6  99.6  81.8 99.5  81.6 99.3  81.3    Example 7           600    6.7  99.8  81.5 99.7  81.4 99.6  81.2    Example 8           570    6.7  99.7  81.9 99.6  81.8 99.5  81.7    Example 9           550    6.7  99.8  81.4 99.7  81.3 99.5  81.1    Example 10           580    6.7  99.7  80.8 99.5  80.5 99.4  80.3    Example 11           590    6.7  99.8  80.5 99.6  80.2 99.4  80.0    Example 12           590    6.7  99.7  81.5 99.5  81.3 99.4  81.1    Example 13           610    6.7  99.6  81.0 99.4  80.7 99.2  80.5    Comp. Ex. 1           610    6.7  99.8  79.8 99.7  79.0 --    --    Comp. Ex. 2           580    5.9  99.9  82.8 99.7  81.2 99.5  78.6    Comp. Ex. 3           610    6.7  99.8  82.3 99.7  81.3 99.6  79.9    Comp. Ex. 4           610    6.7  99.7  76.3 99.5  75.8 --    --    __________________________________________________________________________     Note: "--" means that data were not available because the operation of th     production process was discontinued 700 hours after the start of reaction

EXAMPLE 10

An ammoxidation catalyst composition, composed of oxides supported on50% by weight, based on the total weight of the oxides and silica, ofsilica, having a structure represented by the formula:

    Mo.sub.12 Bi.sub.0.45 Ce.sub.0.90 Fe.sub.2.0 Ni.sub.5.0 Mg.sub.2.0 K.sub.0.45,

was prepared in substantially the same manner as in Example 1, exceptthat the firing was conducted at 610° C. Using 1,000 g of an obtainedcatalyst composition supported on silica, an ammoxidation reaction oftert-butanol was conducted at 430° C. The contact time was 4.8 sec·g/cc.Results of the reaction were evaluated at time points of 100 hours, 700hours and 1,400 hours after the start of reaction. As a result, it wasfound that, 100 hours after the start of reaction, the conversion oftert-butanol was 99.7%, and the yield of methacrylonitrile was 71.9%;that, 700 hours after the start of reaction, the conversion oftert-butanol was 99.6%, and the yield of methacrylonitrile was 71.7%;and that, 1,400 hours after the start of reaction, the conversion oftert-butanol was 99.4%, and the yield of methacrylonitrile was 71.5%.

INDUSTRIAL APPLICABILITY

By use of the ammoxidation catalyst composition of the present inventionin producing acrylonitrile from propylene, or methacrylonitrile fromisobutene or tert-butanol, by ammoxidation of the propylene or of theisobutene or tert-butanol, not only can acrylonitrile ormethacrylonitrile be produced in high yield, but also the ammoxidationreaction can be stably conducted even when the operation of theproduction process is conducted for a prolonged period of time, so thata lowering of the yield of acrylonitrile or methacrylonitrile, relativeto the yield thereof at the initial stage of reaction, is very small.

We claim:
 1. An ammoxidation catalyst composition for use in producingacrylonitrile from propylene, or methacrylonitrile from isobutene ortert-butanol, by ammoxidation of said propylene or of said isobutene ortert-butanol, comprising an oxide catalyst composition represented bythe formula (I):

    Mo.sub.12 (Bi.sub.1-a A.sub.a).sub.b Fe.sub.c Ni.sub.d X.sub.e Y.sub.f O.sub.g                                                   (I)

wherein: A is at least one rare earth element, X is at least one elementselected from magnesium and zinc, Y is at least one element selectedfrom potassium, rubidium and cesium, a is the atomic ratio of A to thesum of bismuth and A, b is the atomic ratio of the sum of bismuth and A,relative to twelve atoms of molybdenum, and c, d, e, f and g are,respectively, the atomic ratios of iron, nickel, X, Y and oxygen,relative to twelve atoms of molybdenum, whereina is a number of from 0.6to 0.8, b is a number of from 0.5 to 2, c is a number of from 0.1 to 3,d is a number of from 4 to 10, e is a number of from 0 to 3, f is anumber of from 0.01 to 2, and g is a number determined by the valencerequirements of the other elements present.
 2. The catalyst compositionaccording to claim 1, wherein A in formula (I) is at least one elementselected from the group consisting of yttrium, lanthanum, cerium,praseodymium, neodymium and samarium.
 3. The catalyst compositionaccording to claim 1, wherein A in formula (I) is cerium.
 4. Thecatalyst composition according to claim 1, wherein b, c, d and f informula (I) are, respectively, from 0.7 to 1.8, from 0.5 to 2.5, from 5to 8, and from 0.02 to 1, relative to twelve atoms of molybdenum.
 5. Thecatalyst composition according to claim 1, wherein e in formula (I) isfrom 0.1 to 2.5, relative to twelve atoms of molybdenum.
 6. The catalystcomposition according to any one of claims 1 to 5, wherein Y in formula(I) is potassium.
 7. The catalyst composition according to any one ofclaims 1 to 5, wherein Y in formula (I) is rubidium.
 8. The catalystcomposition according to any one of claims 1 to 5, wherein Y in formula(I) is cesium.
 9. The catalyst composition according to any one ofclaims 1 to 5, wherein Y in formula (I) is a mixture of at least twoelements selected from the group consisting of potassium, rubidium andcesium.
 10. The catalyst composition according to any one of claims 1 to5, which further comprises silica as a carrier having said oxidecatalyst composition supported thereon, wherein said silica carrier ispresent in an amount of from 30 to 70% by weight, based on the totalweight of said oxide catalyst composition and said silica carrier.
 11. Aprocess for producing acrylonitrile from propylene, or methacrylonitrilefrom isobutene or tert-butanol, by ammoxidation of said propylene or ofsaid isobutene or tert-butanol, which comprises reacting propylene with,or reacting isobutene or tert-butanol with a molecular oxygen-containinggas and ammonia at a temperature of from 350° C. to 550° C. under apressure of from atmospheric pressure to 3 arm in the presence of anammoxidation catalyst composition comprising an oxide catalystcomposition represented by the formula (I):

    Mo.sub.12 (Bi.sub.1-a A.sub.a).sub.b Fe.sub.c Ni.sub.d X.sub.e Y.sub.f O.sub.g                                                   (I)

wherein: A is at least one rare earth element, X is at least one elementselected from magnesium and zinc, Y is at least one element selectedfrom potassium, rubidium and cesium, a is the atomic ratio of A to thesum of bismuth and A, b is the atomic ratio of the sum of bismuth and A,relative to twelve atoms of molybdenum, and c, d, e, f and g are,respectively, the atomic ratios of iron, nickel, X, Y and oxygen,relative to twelve atoms of molybdenum, whereina is a number of from 0.6to 0.8, b is a number of from 0.5 to 2, c is a number of from 0.1 to 3,d is a number of from 4 to 10, e is a number of from 0 to 3, f is anumber of from 0.01 to 2, and g is determined by the valencerequirements of the other elements present.
 12. The catalyst compositionaccording to claim 11, wherein A in formula (I) is at least one elementfrom the group consisting of yttrium, lanthanum, cerium, praseodymium,neodymium and samarium.
 13. The catalyst composition according to claim11, wherein A in formula (I) is cerium.
 14. The process according toclaim 11, wherein b, c, d and f in formula (I) are, respectively, from0.7 to 1.8, from 0.5 to 2.5, from 5 to 8, and from 0.02 to 1, relativeto twelve atoms of molybdenum.
 15. The process according to claim 11,wherein e in formula (I) is from 0.1 to 2.5, relative to twelve atoms ofmolybdenum.
 16. The process according to any one of claims 11 to 15,wherein Y in formula (I) is potassium.
 17. The process according to anyone of claims 11 to 15, wherein Y in formula (I) is rubidium.
 18. Theprocess according to any one of claims 11 to 15, wherein Y in formula(I) is cesium.
 19. The process according to any one of claims 11 to 15,wherein Y in formula (I) is a mixture of at least two elements selectedfrom the group consisting of potassium, rubidium and cesium.
 20. Theprocess according to any one of claims 11 to 15, which further comprisessilica as a carrier having said oxide catalyst composition supportedthereon, wherein said silica carrier is present in an amount of from 30to 70% by weight, based on the total weight of said oxide catalystcomposition and said silica carrier.
 21. The process according to anyone of claims 11 to 15, wherein said molecular oxygen-containing gas isair.
 22. The process according to any one of claims 11 to 15, whereinthe molar ratios of propylene, or isobutene ortert-butanol:ammonia:oxygen are in the range of 1:0.8 to 1.4:1.4 to 2.4.23. The process according to any one of claims 11 to 15, wherein saidreaction is conducted in a fluidized bed reactor.